Impact drill



R. E. SNYDER Nov. 16, 1954 IMPACT DRILL 3 Sheets-Sheet l Filed Feb. l1, 1952 Gttorneg R. E. SNYDER IMPACT DRILL Nov. 16, 1954 5 Sheets-Sheet 2 Filed Feb. ll, 1952 flwhll i D Il Cttorneg R. E. SNYDER IMPACT DRILL Nov. 16, 1954 3 Sheets-Sheet 5 Filed Feb. l1, 1952 4 Illlfllllln flllllllllll. Filli.

Bg t I3 l Gttorneg United States Patent fO IMPACT .DRILL Robert E. Snyder, Pasadena, lCalif., assigner to Snyder v(lil Tool CorporatiomLos Angeles, Calif., a-corporation of California Continuation of application Serial No. 764,975, July 31, This application February 11, 1952, Serial No. S J

Claims. (Cl. Z55-3) `My invention relates generally to drills ofthe type :used in earth boring, and more particularly to such drills that are adapted to provide aseries of impacts to the drill bit as the vdrill is rotated. AThis'applicat-ion is a continuation 4of ymy copending application Serial No. 764.975,;led July 3l, 1947,'now abandoned.

lthas Vlong beenrecognized thatif a'rotating drill bit is periodically caused toimpact against the formation being drilled, a much highereciencyof the drilling operation will be secured. lin my copending application Serial No. 527,179 led March 20, 1944, for an Impact Drill, now Patent No, 2,425,012, issued August 5, 1947, of which this a continuation-in-part, and=in my other applications forlmpactDri'lls, Serial `No.674,526 led lune 5, 1946, now abandoned; Serial No. 714,339, led December 5, 1946, now Patent iNo. 2,635,852; Serial No. 734,989yled March l5, 1.947, -now abandoned; Serial No. 734,990 led March 15,'1'947, now abandoned; and Serial No. 753,941 -filedflune 11, '1947, now abandoned, fl have disclosed various methods'of -securing this'result. yHowever, .assuggested infmy Patent No. 2,425,012 above-mentioned, and as further described and amplified in various of the subsequent applications, the operation of such an 4impact drill-maybe materially improved by the addition of various resilient members such as springs. In some forms, these springs cooperate with other elements of the drill tolprovide a resonant system wherein a maximum of vdrilling eiciency is secured, with a Vminimum of-mechanical energy being expended.

In this .present disclosure, I have described some ofthe forms suggested in Vmy abovennentionedpatent, describing these more fully andv completely and illustrating how they may be modified to secure the other benefits owing from the use of a resilient and of a lresonant system.

lt is a majorfobject of Vmy invention toV provide `an im pact drill adapted for earth boring wherein the=rotary motion of the drill stern is used to provide a series of impacts which are `transmitted to the drill bit to increase the efficiency of the drilling operation.

Another obiect of` my inventiony is' to provide such a drill wherein resilient members are usedv to increase the mechanical efliciency and ease'ofoperation of the impact producing mechanism.

lt is a furtherf object yof'my invention to'provide an impact drill of this general character' wherein the 'properties of a resonant systemare used to reduce the frictionallosses occurring between two relatively rotating members.

`Still another object of my invention is to provide `a drill capable of deliveringa series of rather light impacts at a relatively high rate of speed, as opposed to theV production of heavier impacts at a slower rate of speed.

lt is a still furtherlobiect of my invention to provide such a drill which provides-all the previously mentioned advantages while being simply and ruggedly constructed towihstand the conditions of service to which it will be ut. p These and other 'objects and advantagesl of my invention will become apparent from the following ldescription of the various Yforms thereof, fin which:

Figure 1 is a side elevational View of one form of drill built in accordance with my invention;

Figure 2 is a longitudinal sectional view of the drill shown in Figure l, showing-its `internal construction;

Figure 3 is a cross-sectional view taken at 3 3 in Figure 2;

2,694,551 `Patented Nov. 16, 1954 'Figure 4 is a cross-sectional view taken at 4 4 in Figure 2;

Figure 5 is a longitudinal sectional view of another form of my drill whereinthe rotation producing member s separate from the hammer or impact producing mem- Figure 6 is a cross-.sectional View `taken at 6 6 .in Figure 5 to show the .method of connecting the impact producing member to :the rotation producing member;

Figure 7 is a longitudinal sectional View of another form of my invention in which the relative position of the driving and driven members is reversed;

Figure 8 is a cross-sectional View .taken at 8 :8 in Figure 7 to show the method of attaching the driving member to the shank;

Figure 9 is a cross-sectional view taken at -9-9 in Figure 7 and showing the mounting and connection of the driven member;

Figure 10 is a longitudinal sectional view of another form of my device, based on the form showninzFigure 5, but with a resilient mounting for the impact producing member, operable to provide a resonant system;

Figure 11 Vis a cross-sectional view taken at y1v1-11 in Figure 10, showing -the arrangement of the various concentric members;

Figure 12 is a cross-sectional view taken at l2-12 in Figure 10 to show the mounting and connection of the impact producing member;

Figure 13 is a longitudinalsectional View of a drill similar to that shown in Figure 12 but :based-on the form-shown in Figure 7; and

Figure 1'4 is a cross-sectional view taken at 14-14 in Figure 13 to show theconnectionand yassembly of the impact producing member.

Referring now to ythe drawings, 'and particularly vto Figures l'to 4 thereof, thenumeral 20 indicates generally a shank adapted tube-.attached at itsupper end-to a drill stem or string ofconventional construction (not shown) such `as is wellsknownin theart. At'its lower end, the shank 29 isprovided with atcoupling orconnector 21 adapted 'to-receive a drill bit (not shown) the shank and coupling being provided with a longitudinally'extending hole 22 through which drilling luid.or.mud may be forced in the conventionalmannerto removerock particles-and other-detritus from the lower, end of'the .,well. Immediately above the coupling 2lis: a-n impact receiving member 23 that is rigidly.. connected ,to theshank andthe coupling, and provided with a ,cam-,shaped upper surface 24. The impact receiving member 23, hereinafter referred to as the lower or driving cam, will thus be seen to have a generally tubular .,shape. Upper or driven cam 25 having a lower cam-shaped face,26, complemental to the cam surface .24,.rests upon the driving cam 23 vand is likewise generally tubular in shape.

Rigidly connected tothe uppercam .25 -is a.tubular body 30 having a plurality of radiallyuextending vanes or blades 31 which, in the-form shown, extend longitudinally along the length of .the :body lto engage the drilling fluid within the well. An inwardly projecting shoulder 32 is attached to the upper end of the body 30 to aid in maintaining .the latter. coaxial with the shank 20, while a similar flange or couplingmeans 33 may be provided near themiddleof the cylindrical member to prevent any bowing or whipping of the latter. While the ange 33 mightbe formed as a portion of the cylindrical member 30,.for reasons which will become apparentflater, I prefer to form the ange .asan enlargement 'of the shank20, it being .understood thattthe largest section ofthe flange or coupling maybe covered with rubber or other suitable material whichwill act as an anti-friction bearing surface when lubricated. by the drilling uid. A cross-sectional view taken through'the flange or coupling member-33 is shown in Figure 3.

When the drill is lowered into a well and the shank 20 is rotated, the coupling 21 and the lower cam v23 will be rotated with the shank since they are rigidly connected to it. While 'the upper camlZS and the tubular body 30 are not rigidlyy attached to the shank 20, they will nevertheless be urged to rotate with it because of the friction existing between the cam faces 24 and 26,

and because of the friction between the shank and the collars or flanges 32 and 33.

As the shank 20 is slowly rotated, this frictional engagement will be suflicient to insure that the tubular body 30 will rotate with the shank as though it were rigidly connected thereto. However, as the rotational speed of the shank 20 is increased, the frictional drag of the blades 31 in their passage through the drilling uid will increase until the dragging or restraining torque of the blades becomes sucient to overcome the static friction existing between the cam faces 24 and 26 and the shoulders and collars 32 and 33. When this occurs, the tubular body 30, instead of rotating at the same speed as the shank 20, will be slowed or retarded so that relative rotation will occur between the body and the shank. By reason of the particular shape of the cams 23 and 25, the relative rotation between these cams will cause the upper cam, together with the tubular body 30, to be lifted. When the lobes of the cams override, the upper cam 25 will be released to drop downwardly and impact against the lower cam 23, and this impact is transmitted through the coupling 21 to the bit (not shown) to force the latter into the formation being drilled.

It will be seen that as the tubular body 30 is reciprocated with respect to the shank 20, the coupling or flange 33 will tend to act in a manner similar to a piston therein. However, since it is important that the body 30 be freely movable with respect to the shank 20 at all times, I have provided a series of vent or breather holes 34 in the walls of the body so that any uid therein will not be trapped and retard the axial movement of the body.

Where the mass of the reciprocating member, including the tubular body 30, the vanes 31 and the upper cam 25, is not sucient to produce the desired impact, I mount a helical compression spring 35 between the lower surface of the ange or coupling 33 and' the upper surface of the upper cam 25. When the reciprocable members are in their lowermost positions, the spring 35 is compressed a slight amount to exert a downwardly directed force urging the upper cam into contact with the lower cam 23. As the tubular body 30 is raised by the rotation of the cams 23 and 25, the spring 35 is further compressed until the lobes of the cams override, whereupon the spring aids the force of gravity in starting the downward movement of the cylindrical member and providing a greater impact than would be secured by gravity alone. In this way, the effective mass of the cylindrical member 30 may be quickly and easily changed by merely replacing the spring 35 with one having a different force constant.

Description of F gures and 6 In Figures 5 and 6 I have illustrated another form of my invention which is quite similar to that shown in Figures l to 4, but which is so designed that the tubular body 30 does not reciprocate but instead remains substantially axially immovable while benig free to rotate with respect to the shank 20. The upper or driven cam, however, while rotating with the tubular body 30, is axially reciprocable with respect thereto so that this cam acts as the impact member when the drill is being operated.

Considering this form in somewhat greater detail, it will be seen that it includes a central shank having a coupling member 21 at its lower end to which a drill bit 40 is attached in the customary manner. the shank and connector having a longitudinally extending hole 22 therethrough adapted to carry drilling uid. Mounted on the upper end of the connector 21 is a driving cam 23 having an upper cam surface 24 on which rests an upper or driven cam a having a lower cam surface 26. Like the driven cam 25 previously described, the driven cam 25a is rotatably and reciprocably mounted on the shank 20, and is connected to a tubular member a generally similar to the tubular body 30 previously described, but differing in several important respects therefrom.

Near its upper end, the tubular member 30a is provided with an inwardly extending shoulder 41 adapted to bear against a cooperating outwardly extending collar or flange 42 mounted on the shank 20. As indicated, the upper surface of the shoulder 41 bears against the lower surface of the collar 42 to prevent any upward movement of the tubular member 30a, and downward movement is prevented by a helical compression spring 35 which bears against the lower surface of the shoulder 41 and against the upper surface of the upper cam 25a. The upper end of the driven cam 25a is reduced in diameter to form a shoulder 44, and the lower end of the tubular member 30a is spaced a sufficient distance above the shoulder so that the cam may move its full distance upwardly without hitting the lower end of the tubular body. The reduced section 43 extends upwardly within the tubular member 30a and is provided with splines or keys 45 adapted to tit within slots or grooves 46 formed in the tubular member 30a so that rotational motion may be transmitted from the tubular body to the cam 25a, while leaving the latter free to reciprocate with respect to the tubular body.

To complete the device, the tubular body 30a is provided with fluid engaging vanes or blades 47 which project radially outwardly from the body as do the blades 31, but instead of extending parallel to the axis of the shank 20, the blades 47 are given a helical form and thus wind around the tubular body 30a. In Figure 5 I have shown the blades 47 as having a lefthand pitch and thus as the tubular member 30a is rotated in a clockwise direction as viewed from above, the action of the blades on the drilling fluid will be such as to tend to lift the tubular body and thereby support a portion of the weight normally carried by the spring 3S.

In the operation of this form of my device, the drill is lowered into a well and the shank 20 is rotated while drilling uid is forced down the hole 22 to escape through holes 50 in the bit 40 near the blades thereof. The fluid then returns upwardly in the space between the body 30a and the wall of the hole, carrying with it the detritus formed by the operation of the drill. As the speed of rotation of the shank 20 is increased, the retarding action of the vanes 47 becomes greater until finally the driven cam 25a starts to rotate with respect to the driving cam 23. When this occurs, the driven cam 25a is moved upwardly, the keys 45 moving similarly within the slots 46, until the lobes of the cams override, whereupon the upper cam, under the inuence of gravity and of the spring 35, quickly moves downwardly to impact against the lower cam 23.

Since substantially the entire weight of the tubular body 30a is carried by the spring 35, this downwardly directed force will be applied to the driven cam 25a and hence the latter will be caused to impact against the lower cam 23 with a force which is derived from the weight of the upper cam, the weight of the tubular body 30a, and the compression of the spring 35. However, since the mass of the reciprocating member, the upper cam 25a, is relatively small, the rate at which impacts may be delivered to the lower cam 23 may be made quite high While the impetus of each of these impacts may be kept at a substantial amount.

Description of F gures 7 to 9 In my previously described forms, the cam connected to the shank 20 has been the lower or impact receiving cam, while the cam connected to the cylindrical body has been the upper or impact producing cam. This particular arrangement of parts is not essential to the operation of my device, and in Figures 7 to 9 I have illustrated one form in which the relative positions of these two cams has been interchanged. In this form, a shank 20 is provided with a coupling member 21 at its lower end adapted to receive a bit 40, and the shank and coupling member are provided with a longitudinally extending bore 22, all as previously described.

Mounted on the upper end of the coupling 21 for rotation with respect thereto is a driven or impact receiving cam 51 having an upper cam surface 52. A driving or impact producing cam 53 is slidably mounted upon the shank 20 above the driven cam 51, and is provided with a lower impact surface 54. The driving cam 53 is connected by splines or keys 55 to the shank 20 for rotation therewith and for reciprocation with respect thereto, while the driven cam 51 is rigidly connected to a tubular body 30h similar to the tubular body previously described.

Near the upper end of the tubular body 30b I provide a coupling 42 or other similar means on the shank 20 to hold the tubular body concentric with the shank, and to act as a shoulder for a helical compression spring 35 whose upper end bears against the lower end of the cou- .gcarriedfdirectlyfby the coupling 21; Whilethefdrivingcam '53 :is urgedfv downwardly, into: contact with thedrivencam, Eby: the zweight. of 'the former. and .by the? force ofithe 'spring 35. Helical blades'47a,.:similar. tofthe'blades! 47 :previouslylmentioned but having aL `reversefpitch .therefrom, are attached to the,l outer ysurface :ofrthe -tubular `body:30b,-.and act `to-retardv the rotationxof` thentubular body witlrfrespectto theshanletwhen the :latter is rotated `within -.a yWell. having` drillingifluid therein.

`As relative rotationbetween'rthe tubular bodyfb-and the shank o.ccurs,:the driving cam moves upwardly, compressing..the..spring,35;untilxsuch time as the-lobes of .thecamsoverride/:whereupon `the spring'and the force of gravitya move'` the camv downwardly. to impact` against the `lowerf driven: cam 51,;this1impact being 1transmittedto 'the bit 40.

In .this .form,"the,tubular body 30h doesnotreciprocate but instead retains its same axialposition with -respect lto -thewshank 21),..wliilev rotatingy .with respect thereto. The vweight-ofthe rotating members is carried by the coupling v21,l Iwhile, lthe ,mass of the reciprocating or=impact producing memberl 53:y is` relatively. small. Consequently, the' frequency; of the impactsidelivered by this drill maybe much higher :than .those of thepreviously describeddrills, but t-wilkberealized:that1theenergydelivered by each single impact willbe .considerably less. i However; by using the spring 35 inthe manner illustrated, the energy of fthefindividual impacts 1may :be: considerably'increased, and 'this ofcoursemayzbe,varied over. ratherwide? limits byf-replacing the` springl35 withone .Whichhasadiiferent force constant. lt-will`belnoted thatnoneof the external-parts of athis: formi of my; :invention reciprocate `with respect to thezishank,vv and athis feature `may be- .of' considerable value in certainy applications.

J Description of' Figures 10 to`12 is provided with1;asection"43 of reduced diameter having keys-145 therein adaptedxtoi fit-in slots-46 formedl in the tubular body. 'Fluid dragzmeans'lare4 mounted on thez=outer-= surfacev ofthe tubular membertla, fthough it will'bev apparent that. otheri.forms,1such as the yhelical blades 47'f-or147a shown inFigUres-S and'7,respectively,

may-befusedif so desired.

' While tlleztubularl bodyavmay be` supported [directly by .suitable :flanges Vor collars `on the- .shank= 20,' 4inFigure 10; I .have illustrated .az resilient supportI forftheftubular bodynwhich helpsiin'decreasingzthefriction existing between the tubular body andiithewshank'so thatfthei-body is more freely rotatable thereon. To provide this resilient support; Izrnount. an .inwardly extending shoulder =member 60 near the upperendofthe .tubular body 30a, and provide cooperating 'Ranges or collars 61 and 62 on the shrank` 20 above and below the shoulder of the tubular body. Theilangesl and` 62are spaced" from the shoulder` 60,-and between .thesemembers Ii-insert helical compression springs63..and 64. .Thelower spring-lcarries the=entire weightof the .tubular bodya, and theupper spring..63\ac ts asabumper to; prevent lthe tubularbody from being .raiseda considerable distance' above the counterbalancing .spring 64. .In thisway, a resilient support for, the tubularbody..30a is .provided,-and in the-'normal course of its operation, there will be a considerable longitudinal vibration of the body which, as is well known, will tend to reduce the frictional drag between the body and the shank 20.

Extending upwardly from the reduced section 43 of the driven cam a is a tubular extension 65 which just clears the inner wall of the tubular body a and is spaced from the outer wall of the shank 20. A flange 66 is formed on the shank 20 substantially midway of the extension 65, clearing the inner surface of the extension so that the latter is freely movable with respect to the shank Cil) :20. .fAt :its:upper:end,'itheeextensiom65;.=isv provided with ani mwardlyeprojecting shoulder.l` 67 thatf V`is .fspacedfrom :thezzsha'nk 20,',1the..'shoulder. itherebyf forming an enclosed @compartment betweenitsiunder'surface andathe upper surface oftthe reducedfsection`v 43.

Withinlthe space "between thel shoulderf 67 tand '.the

ange 66,' I :mount: ahelical compression ,spring'701 adapted'.tosupport"thefweight of the driven cam25a and the membersf. attachedfthereto, :and between thei liiange and -thefupper surface .of .fthe reduced section? 431 I-mount another; helical `compressionfspringf71 vopposing thezaction of the spring 70 and acting to movezl'the` camdownwardly.

`By this method of mounting theimpactproducing cam 25a, .itwwillfbe: seen :thataresilient support isfprovided vwhich -is.capable 'tofwmechanical resonance. The. use of the resonantnsuspension,asdiscussedin some of my' previously'mentioned co-.pending applications,.-results ina system `which providessa maximum-.of fimpactenergy for aminimum of rotational energy.

:The*operation:of this formof my linvention is'essentially similar to thatzof'thelformr` shown in Figs. 5 and 6, with the. exception that theimpact producing cam`25a is zsupportedwbyv a double `spring.arrangement-instead of the single springwarrangementfof fthe previous form, and hence the resonantuoperationoffthe presenti form is more easily secured. :.Since thezweightofthe tubular body-30a isrfnot carriedl'byztherimpact producing cam 25a,- the staticvforcessurging thatl cam into contact'with 'the impact receiving cam 23 will normally be smaller, and the friction existing between the cam faces 24 and 26 will like- .wisebeareduced 'lhismeans that therewill belesstorsional orrotationalwforce :required to startthe upper cam oscillatingfwhile :the frequency and. impetus of the -irnpactsA produced :thereby` maynbe` readily controlled bythe selectionrof'zthe: springs 70 and 71.

YIn addition, the :resilient mountingtofthe tubular body 30a meansthatdhetnormal `vibration caused-by the impacts prodncedrby..thezcamsiis transmitted yto the tubular body:;inf:such3;airnanner thatthe vvibrations tend to cause a;slight and' momentary separation .ofthe various bearing faces so that rotation. of `one .of theV faces-with respecty toitherotherzais;more: easily produced. "Consequently,1a;.more :'eflicient. operationy is i obtained, and a smallerfbladenarea'maybe'used, or thespeed at which impacts .rst ioccur awill be reduced.

rAsfthe formshown in IFigs. 5=1and.6may be-rnodied to;producefthet formftshown in Figs.' -10 to 12, so the form -shownzirrFigs 7 tof9'maybe modified-to produce the form- `showninFies.. 13 .and 14. 2l In this form, as in the.fformshownvin='Figs. 7,8 andf9,.a 'shank 2i) isprovided'with` a. cc-nnectorl;21,.a lower, vdriven, impact receiving-.;camw51, fanupper, :.driving, impact` producing cam 53a, tand; aiftubular body tlbfprovidedv with fluid engagingifvanes 31, all .askin my previously described form. :fln addition,f keysf55..are mounted inthe upper cam 53a to engage correspondingf'slots in the 4shank 20, whileeawresilientSfsupportifor the tubular: body'ilb is providedwsimilaruto*thatf shown inrFigs. l0 and' l2, including'collari andranges` 60;.61 and.62fand helical compression springs 63 and 64.

vsnl-.roundingtfthegshank 20. andextending upwardly from the driving carnr53azis aitubular'extension 30 which carries-.an 'outwardly extendingzcollar i811. on its upper end, ,while-.aninwardly projecting VshoulderZ is attached to the 4inner snrfaeebf the`bodyi30b at a'point approxi- Inatelyrnidwayl bewteen-thercollar Sland the upper surface-ofthedrivingcam 53a. A helical compression spring 7 0 is 'mounted' between the collar 81 and yshoulder 82, v while'. a similar-.spring -71 is tinserted lbetween the shoulder-.and lthe upper surface of the` driving cam 53a.

JIn .this '-forrn. of.;my device, 'itcwillV bea-noted that the upward movement of the driving cam 53a tends to move the tubular bodv 30h upwardly by reason of the compression of the spring 71, while the motion of the body is restrained or prevented by its attachment to the driven cam 51. However, when the lobes of the cams 51 and 53a override each other, the spring 71 tends to move the body upwardly while moving the driving cam downwardly, but at this instant there is no restraining force exerted upon the cam 51 and hence the tubular body and the driven cam will tend to rise a slight amount. The movement of the tubular body 30b will be much less than the movement of the driving cam 53u because of the much greater mass of the former. However, any movement of the tubular body 30b upwardly will cause the driven cam 51 to be lifted from the upper surface of the coupling member 21, and hence the impact between the driving cam and the driven cam will occur in mid-air, so to speak, and will not be transmitted directly to the coupling member 21. This condition is obviously undesirable, and hence in this form of my drill the helical compression spring 63 extending between the shoulder 60 of the tubular body 30b and the flange 61 of the shank is made quite stii.

In the type of drill shown in Fig. lO, it should be noted that the impact producing cam is resiliently connected to the shank 20, while in the presently described form, the impact producing cam is resiliently connected to the tubular body. In all of these forms, however, the impact producing member is resiliently mounted in such a manner that mechanical resonance may be established so that the maximum advantage may be secured from the use of a relatively lightweight hammer means producing impacts at a fairly high frequency.

From the foregoing, it will be apparent that these and other modifications may be made in the various forms of the drill which I have shown herein. All of these modications however, fall within the scope of my invention as herein defined, and I do not wish to be restricted to the particular form or arrangement of parts herein described and shown except as limited by my claims.

I claim:

1. An impact drill which includes: a shank rotatable in a hole having drilling uid therein, and having a bitreceiving member attached thereto; a driving cam attached to said shank for rotation therewith; a driven cam mounted on said shank for longitudinal and rotational movement with respect thereto, said cams cooperating to raise said driven cam and then release it to impact against said driving cam when relative rotation occurs between said cams; a tubular body mounted on said shank for rotational movement with respect thereto, said body being connected to said driven cam for movement therewith; retarding means mounted on said body and movable therewith to reduce the speed of rotation of said body, whereby the latter and said driven cam are caused to rotate with respect to said shank while remaining rotatable with respect to the wall of said hole; a collar mounted on said shank, spaced from said driven cam; a tubular extension attached to said driven cam and extending upwardly therefrom, said extension surrounding said collar, and spaced from the latter and from said body; an inwardly extending shoulder attached to the upper end of said extension; a helical compression spring mounted between said shoulder and said collar to urge said driven cam upwardly; and a second helical compression spring mounted between said collar and the upper end of said driven cam to urge the latter downwardly, whereby a resonant suspension is provided for said driven cam.

2. A drill as described in claim 1 in which said body is mounted on said shank by a pair of resilient helical compression springs to provide a resonant support for said body.

3. An impact drill which includes: a rotatable bitreceiving shank; a body mounted on said shank for rotation with respect thereto; blade means on said body positioned to engage said iluid and retard the rotation of said body with respect to said shank while said body remains rotatable with respect to the wall of said well; an impact member mounted on said shank for longitudinal reciprocation with respect thereto; collar means on said shank above said impact member; resilient means between said collar means and said impact member urging said impact member downwardly; over-riding cam means operated by the relative rotation of said body with respect to said'shank to lift said impact member and then release it, whereupon said impact member is moved downwardly by gravity and by said resilient means to produce an impact which is transmitted to said bit; and spring means between said collar means and said impact member urging the latter upwardly against the force of said resilient means whereby a resonant suspension is provided for said impact member.

4. An impact drill which includes: a bit-receiving shank rotatable in a well having iluid therein; a body mounted on said shank for rotation with respect thereto; blade means on said body for engaging said uid to retard the rotation of said body with respect to said shank while said body remains rotatable with respect to the wall of said well; an impact member mounted on said shank for longitudinal reciprocation with respect thereto; resilient means between said shank and said impact member urging Said impact member downwardly; 'a lower cam; and an upper cam attached to said impact member, one of said cams being connected to said shank for rotation therewith, and the other of said cams being connected to said body for rotation therewith, whereby relative rotation between said shank and said body causes said cams to over-ride, lifting said impact member against the urging of said resilient means and then releasing said member to cause an impact to be delivered to said bit; and spring means between said shank and said impact member urging the latter upwardly whereby a resonant suspension is provided for said impact member.

5. An impact drill which includes: a bit-receiving shank rotatable in a well having drilling fluid therein; a body mounted on said shank for rotation with respect thereto; a blade mounted on said body to engage said iluid and thereby retard the rotation of said body with respect to said shank, whereby relative rotation between said body and said shank is produced while said blade remains rotatable with respect to the wall of said well; an impact member mounted on said shank for axial and rotational movement with respect thereto, said impact member being connected to said body for rotation therewith, but axially movable with respect thereto; a collar xed to said shank above said impact member; spring meansbetween said collar and said impact member urging said impact member downwardly; a lower cam connected to 'said shank for rotation therewith and substantially immovable axially with respect thereto; an upper cam connected to said impact member for rotation therewith, said upper and lower cams cooperating to raise said upper cam and said impact member against the urging of said spring means and then release them to impack against said lower cam when rotation occurs between said body and said shank to transmit an impact to said bit, said spring means acting to increase the force of said impact; a tubular extension attached to said upper cam and extending upwardly therefrom and above said collar; shoulder means on the upper portion of said tubular member above said collar; and a compression spring between said collar and said shoulder means urging said impact member upwardly whereby a resonant suspension is provided therefor.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,112,498 Van Es Oct. 6, 1914 1,745,351 Bishop Feb. 4, 1930 1,821,212 Granger Sept. 1, 1931 1,899,438 Grant Feb. 28, 1933 2,241,712 McNamara May 13, 1941 2,287,157 Woli June 23, 1942 2,371,248 McNamara Mar. 13, 1945 2,425,012 Snyder Aug. 5, 1947 

